/*
 * Hivemall: Hive scalable Machine Learning Library
 *
 * Copyright (C) 2015 Makoto YUI
 * Copyright (C) 2013-2015 National Institute of Advanced Industrial Science and Technology (AIST)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package hivemall.tools.mapred;

import static hivemall.utils.hadoop.WritableUtils.val;
import hivemall.utils.hadoop.HadoopUtils;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.hive.ql.udf.UDFType;
import org.apache.hadoop.io.Text;

@Description(name = "rowid", value = "_FUNC_() - Returns a generated row id of a form {TASK_ID}-{SEQUENCE_NUMBER}")
@UDFType(deterministic = false, stateful = true)
public class RowIdUDF extends UDF {

    private long sequence;
    private int taskId;

    public RowIdUDF() {
        this.sequence = 0L;
        this.taskId = -1;
    }

    public Text evaluate() {
        if(taskId == -1) {
            this.taskId = HadoopUtils.getTaskId() + 1;
        }
        sequence++;
        String rowid = taskId + "-" + sequence;
        return val(rowid);
    }
}
